Know The Different Types Of Glass Out There When Learning How To Replace Window Glass

There are lots of different types of glass for windows available when learning how to replace window glass or fix a broken window and below is a brief description of the common ones.

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Standard clear glass for windows
This glass was the first and only type to be installed in millions of houses throughout the years and is fast being replaced with more thermally efficient versions.

Low E/K window glass
This improved glass (in comparison to Standard glass) has an increased environmental performance with less CO2 emissions and better thermal efficiency and nowadays it is compulsory (to comply with Building Regulations) to put Low E/K Glass for windows into NEW houses. It is also good practice to try and replace windows in existing houses with Low E / K glass but this is not always practical. The reasons being that K glass has a slight tint to it and it will not match the rest of the property if the remaining windows has standard glass. But, if you upgrade all your windows to the more efficient K glass, you will benefit from reduced energy bills.

You will obviously only replace them all for K glass if quite a few of your existing windows have already broken down.

Both of the above types of glass, including patterned glass can come as Toughened Glass.

Toughened glass is exactly what it is described as – toughened or tempered.  It has been manufactured by controlled thermal or chemical treatments to increase its strength compared with normal glass. It will usually shatter into small fragments instead of sharp shards when broken, making it less likely to cause any injury if smashed.

From The Building Regulations 2000 – Safety In Relation To Impact, Opening & Cleaning
Approved Document N

Critical locations
In some areas and at certain heights, toughened glass will be required to be used and the best place to check all this information is in the above Building Regulations and this can be downloaded Free Of Charge at:

This website address was correct at the time of this report being published.

For information only, these ‘critical areas’ are generally between finished floor level and 800mm above that level in internal and external walls and partitions AND between finished floor level and 1500mm above that level in a door or in a side panel, close to either edge of the door. Please refer to the Approved Document N (as mentioned above) and you will see clear diagrams in the Building Regs detailing this.

It would be true to say that qualified Window fitters when replacing glass for windows replace like for like i.e. whatever glass is taken out is replaced new with the same. Most of the time this will result in the correct type of glass being installed but they are relying on the person who installed before them getting it right so it is always worth checking that the right window glass was previously installed.
It is strongly advisable to get a copy of The Building Regulations 2000 – ‘Glazing – safety in relation to impact, opening and cleaning’ Approved Document N. This can be bought online at for £7.50 or you can download for free on:

It can be hard to assess what type of glass it is currently in the frame at a glance. If it does have a kite mark on it,
it is more likely to be toughened glass but this should not be left to chance.

Pattern or Plain Glass For Windows
Glass suppliers will have a brochure of all the different patterned glass they supply and you will come across lots of various patterns out there.

It is however, always recommended that you use a qualified Window fitter to replace your Double Glazed (DG) panes. Even though a straightforward task, if you do your own, you undertake the task at your own risk.

If you are fed up with staring at a misted up or broken Window or Double Glazed unit, please click REPLACE DOUBLE GLAZING to grab a FREE 19 Page Report and you will get EVERYTHING you need to know to replace you Double Glazed units TODAY.